Media Gateway Control Protocol (MGCP), is RFC2705 Protocol of the Internet Engineering Task Force (IETF), and Media Gateway Control (MEGACO) is RFC 3015 Protocol of IETF. Media Gateway Control Protocol (MGCP/MEGACO) is a protocol between soft switch equipment and media gateway for controlling action of media gateway.
With an idea of discomposing gateways, MEGACO/MGCP protocol discomposes original gateways processing signalling and media stream into two parts: media gateway (MG) and media gateway control (MGC). A physical logic entity on MG can be identified with endpoints, as shown in FIG. 1. A MGC controls action of a MG through MEGACO/MGCP Protocol, and processes requests submitted by a MG; a MG mainly processes information of media stream. Both MGC and MG are network elements in a network, and communicate with each other through MEGACO/MGCP Protocol.
Due to decomposition of MGC and MG, a MGC can control action of multiple MGs, and sometimes such situation may happen that a MGC and MGs controlled by it locate in different networks and thus an agent equipment is needed to realize signalling agent for MGC's controlling on MGs.
A signalling agent means to realize, by a signalling agent, traversing MGCP/MEGACO signalling and media stream controlled through networks, where MGC and MGs are in different networks and can not be reachable to one another by routes, so as to make MGC enable to control MGs in other networks completing call establishing and media stream intercommunicating.
Agent equipment is independent equipment, which provides signalling and media stream agent function among networks in a packet switching network and takes charge of providing signalling and media stream agent between different networks and network address translation.
At present, a common method for realizing signalling agent among different networks is based on network address translation (NAT), but in this method agent equipment cannot make MGC entirely transparent, and complexity for realizing call services on MGC is increased; meanwhile detailed information on corresponding MG needs to be configured on the agent equipment, and, thus, any change on MG under control of MGC requires informing the agent equipment to change configuration, which increases operation maintenance cost.